Identification of shunts in a monolithic multijunction GaAs/GaAs device by spectrometric characterization

Monolithic multijunction solar cells are one of the most promising concepts for future, high-efficiency commercial solar cells. However, the characterization of this type of device, and the identification of detrimental mechanisms such as shunts, tends to be complex compared to single junction devices. In this work, we propose a methodology to identify the shunted subcell in monolithic multijunction devices by spectrometric characterization and equivalent circuit modelling. Current-voltage (J-V) characteristics of a GaAs/GaAs dual junction solar cell are measured under different spectra and constant intensity. A series-connected, two-diode equivalent circuit model is developed, and the shunted subcell in the tandem stack is identified by fitting the measured data. The J-V characteristics for different spectra and the effect of shunts on them are explained.